(a) Field of the Invention
The present invention relates to a key depression indicating device for an electronic musical instrument, and more particularly it pertains to a key depression indicating device for a keyboard type electronic musical instrument having a plurality of keys and tone-producing channels, which device having a plurality of key depression indicators corresponding respectively to said keys and being selectively lighted up in accordance with the note data read out from memory means sequentially, whereby to indicate keys requiring successive depressions with the progression of a music piece so that a trainee may effect a musical performance by following the key depression indications.
(b) Description of the Prior Art
In the field of monophonic electronic musical instruments, there has been known the art which is designed to indicate those keys requiring to be depressed one after another as the indicators are lighted up successively in accordance with the note data read out from memory means which are provided in the instrument (see, for example, U.S. Pat. No. 4,378,720). In this prior art, arrangement is provided so that, under the condition that the key corresponding to a given note has been depressed actually, an indicator corresponding to the next note is lighted up.
In a polyphonic electronic musical instrument also, there has been known the technique which is similar to that of the above-mentioned monophonic electronic musical instrument and which is designed to be operative so that, under the condition that a plurality of keys corresponding to a given chord, e.g. C-E-G, have been actually depressed simultaneously, a plurality of key depression indicators corresponding to the next chord are lighted up simultaneously, whereby indicating the chord keys which are to be depressed next (see for example, Japanese Patent Preliminary Publication No. Sho 59-90894).
According to the above-mentioned prior art, there are the following inconvenience such that, while in case the note of the depressed key is a relatively long one such as a half-note, the illumination by the key depression indicator corresponding to the next note commences a certain period (for example, a time length corresponding to a fourth note) ahead of the arrival of the timing for the depression of said next key, and that this indicator is kept illuminating till the arrival of the timing for the depression of said next key; in case, however, the note of the depressed key is a relatively short one such as a 32nd note, the indicator corresponding to the next note is lighted up only for a short period corresponding to the duration of the short note of the key depressed just now. For this reason, in case there occurs a train of a plurality of consecutive short notes, no sufficient key-depression indicating time is available, giving rise to the problem of hampering a smooth key depressing operation.